1. Technical Field of the Invention
The present invention relates to a supercharger.
2. Description of the Related Art
A supercharger is provided with a turbine and a compressor as a basic structure, the turbine has a turbine impeller rotationally driven by an exhaust gas of an engine, and the compressor has a compressor impeller rotationally driven by a rotation of the turbine impeller. Further, in order to transmit a rotational driving force from the turbine to the compressor, a rotating shaft coupling the turbine impeller and the compressor is provided in the supercharger.
On the basis of the structure mentioned above, the turbine impeller is rotated by the exhaust gas of the engine, the compressor impeller is rotationally driven therewith, and the compressed air is supplied to the engine from the compressor. Accordingly, a supercharged state equal to or more than a natural air supply is achieved in the engine, and the engine is set to a high-power state.
In order to rotatably support the rotating shaft mentioned above, a bearing structure is incorporated in an inner portion of a housing of the supercharger, and an oil seal structure is incorporated in a compressor side of the bearing structure for preventing a lubricating oil supplied to the bearing structure from leaking to the compressor side.
The bearing structure and the oil seal structure mentioned above are disclosed, for example, in patent document 1.
FIG. 1 is a vertical cross sectional view showing an entire structure of a supercharger in the patent document 1, and FIG. 2 is a partly enlarged view of FIG. 1, and shows a bearing structure and an oil seal structure.
As shown in FIG. 2, the bearing structure has a thrust bush 33 fixed to a rotating shaft 31, a normal thrust bearing 37 positioned in a compressor side of the thrust bush 33 and fixed to a bearing housing 35, and a counter thrust bearing 39 positioned in a turbine side of the thrust bush 33 and fixed to the bearing housing 35. Further, the bearing structure has a journal bearing 41 provided in each of the turbine side and the compressor side.
The normal thrust bearing 37 and the counter thrust bearing 39 receive an axial load from the rotating shaft 31 via the thrust bush 33, and the journal bearing 41 receives a radial load from the rotating shaft 31.
In order to supply a lubricating oil to the bearing structure mentioned above, an oil path 43 is formed in the housing, and a dedicated oil path 45 communicating with the oil path 43 and open only to a pad surface thereof is formed in the normal thrust bearing 37.
In order to prevent the lubricating oil supplied to the pad surface through the oil path 43 and the dedicated oil path 45 from leaking to the compressor side, an oil seal structure is provided in the compressor side of the bearing structure.
The oil seal structure has an oil shield member 47 fitted to the rotating shaft 31 in the compressor side of the normal thrust bearing 37.
In the oil shield member 47, a flange portion 47a is formed in an end portion in the turbine side, and one ring groove 47b is formed on an outer peripheral surface in the compressor side in a peripheral direction. An annular seal member 49 is fitted to the ring groove 47b. The seal member 49 is formed, for example, by a metal.
Further, the oil seal structure further has an oil defense plate 51 fixed to the housing in the turbine side of the normal thrust bearing 37.
The oil defense plate 51 is constituted, for example, by a disc-shaped thin plate, has a shape in which a lower portion is folded up to the turbine side, and introduces the lubricating oil after lubricating the normal thrust bearing 37 to an oil discharge port 55.
Further, the oil seal structure has a seal housing 53 fixed to the housing 35 in the compressor side of the oil defense plate 51. The seal housing 53 extends to an inner side in a radial direction from an outer side in a radial direction to a position brought into contact with the seal member 49, and is brought into contact with the seal member 49 mentioned above over a peripheral direction.
Accordingly, it is possible to prevent the lubricating oil from leaking to the compressor side from the seal housing 53.
Patent Document 1: Japanese Unexamined Utility Model Publication No. 4-119624 “bearing structure of turbocharger”
In the oil seal structure in the patent document 1, since the seal member 49 is formed in the annular shape, it is necessary to fit it to the ring groove 47b from an outer side in the radial direction, for attaching it to the ring groove 47b. Further, it is necessary to attach the seal member 49 before incorporating the seal housing 53 in the supercharger, and it is impossible to attach the seal member 49 later. Accordingly, an inconvenience is generated.
As mentioned above, in the patent document 1, a workability at a time of attaching the seal member 49 is deteriorated.
Further, a structure having a higher sealing performance than the oil seal structure in the patent document 1 is desired.